What is M2 Browning Machine Gun?

M2
An M2 machine gun surrounded by spent cartridge cases
Type	Heavy machine gun
Place of origin	United States
Service history
In service	1921 M2 from 1932–present
Used by	See text
Wars	World War II, Cold War, Falklands War, Desert Storm, Iraqi Freedom
Production history
Designed	1921
Produced	1932–
Specifications
Weight	38 kg (58 kg w/ tripod)
Length	1,650 mm (65 in)
Barrel length	1,140 mm (44⅞ in)
Cartridge	.50 BMG
Action	Recoil-operated; short recoil
Rate of fire	Sustained: < 40 rds/min, in bursts of five to seven rounds Cyclic: 450-550 rds/min
Muzzle velocity	3,050 ft/s (930 m/s)
Effective range	1,800 m (2,200 yd)
Feed system	Belt-fed

This article is about the .50 caliber M2 machine gun. For the .30-06 M2 machine gun, see M1919 Browning machine gun.

The M2 Machine Gun, or Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the end of World War I by John Browning. It was nicknamed Ma Deuce by US troops or simply called "fifty-cal" in reference to its caliber. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly-armored vehicles and boats, light fortifications, and low-flying aircraft.

The Browning .50 machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1920s to the present day. It was heavily used during World War II, the Korean War, the Vietnam War, as well as during operations in Iraq in the 1990s and 2000s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. It is still in use today. It was very similar in design to the smaller Browning Model 1919 machine gun.

History

Using a round originally designed by Winchester, the .50 BMG round was designed as a response to the German 13 mm anti-tank rifle of World War I and employed in a redesigned and scaled-up M1917 Browning .30 cal. machine gun. It was quickly adapted to the anti-aircraft role. It was also selected for the ground role and adopted by the U.S. as the Model 1921. The latter served during the 1920s as an anti-aircraft and anti-armor gun. In 1932, the design was updated and adopted as the M2, though fulfilling the same role. As with the M1921, the original infantry variant of the M2 was equipped with a water jacket for cooling [1]. A variant without a water jacket, but with a thicker-walled, air-cooled barrel superseded it (air-cooled barrels had already been used on variants for use on aircraft, but these quickly overheated in ground use). The added mass and surface area of the new barrel compensated, somewhat, for the loss of water-cooling, while reducing bulk and weight (the M2 weighed 121 lbs, with water, whereas the M2 HB weighs 84 lbs). This new variant was the designated the M2 HB (HB for Heavy Barrel). Due to the long procedure for changing the barrel, an improved system was developed called QCB (quick change barrel). A lightweight version, weighing 24 lb (11 kg) less—a mere 60 lb (27 kg)—was also developed.

Design

The M2 is a scaled-up version of John Browning's M1917 .30 caliber machine gun (even using the same timing gauges), and fires the .50 BMG cartridge, which today is also used in high-powered sniper rifles and long range target rifles due to its excellent long range accuracy, external ballistics performance, incredible stopping power, and lethality. The M2 is an air-cooled, belt-fed, machine gun that fires from a closed bolt, operated on the short recoil principle. In this action, the bolt and barrel are initially locked together, and recoil upon firing. After a short distance, the bolt and barrel unlock, and the bolt continues to move rearwards relative to the barrel. This action opens the bolt, and pulls the belt of ammunition through the weapon, readying it to fire again, all at a cyclic rate of 450–550 rounds per minute (600–1,200 M2/M3 in WW2 aircraft, 300 synchronized M2). This is a rate of fire not generally achieved in use, as sustained fire at that rate will "shoot out" the barrel within a few thousand rounds, necessitating replacement. The M2 machine gun's sustained rate of fire is considered to be anything less than 40 rounds per minute.

The M2 has a maximum range of 7.4 kilometers (4.55 miles) when using the M2 ball ammunition, with a maximum effective range of 1.8 kilometers (1.2 miles) when fired from the M3 tripod. In its ground-portable, crew-served role, the gun itself weighs in at a hefty 84 pounds (38 kg), and the assembled M3 tripod another 44 pounds (20 kg). In this configuration, the V-shaped "butterfly" trigger is located at the very rear of the weapon, with a "spade handle" hand-grip on either side of it and the bolt release the center. The "spade handles" are gripped and the butterfly trigger is depressed with one or both thumbs. When the bolt release is locked down by the bolt latch release lock on the buffer tube sleeve, the gun functions in fully automatic mode. Conversely, the bolt release can be unlocked into the up position resulting in single-shot firing (the gunner must press the bolt latch release to send the bolt forward). In either mode the gun is fired by pressing the butterfly triggers. Recently new rear buffer assemblies have used squeeze triggers mounted to the hand grips doing away with the butterfly triggers.

Because the M2 was intentionally designed to be fit into many configurations, it can be adapted to feed from the left or right side of the weapon by exchanging the belt-holding pawls, the belt feed pawl, the front and rear cartridge stops, and reversing the bolt switch. The conversion can be completed in under a minute with no tools.

When firing blanks, a large blank-firing adapter (BFA) must be used to keep the gas pressure high enough to allow the action to cycle. The adapter is very distinctive, attaching to the muzzle with three rods extending back to the base. The BFA can often be seen on M2s during peacetime operations.

Combat use

The M2 .50 Browning machine gun is used for various roles:

• A medium infantry support weapon
• When doubled it is used as an anti-aircraft gun in some ships, or on the ground. In these cases, one M2 with a left-handed feed and one with right-handed feed are paired. Four and six guns are also sometimes mounted on the same turret.
• Primary or secondary weapon on an armored fighting vehicle.
• Primary or secondary weapon on a naval patrol boat.
• Secondary weapon for anti-boat defense on naval destroyers, frigates and aircraft carriers.
• Coaxial gun or independent mounting in some tanks.
• Fixed-mounted primary armament in World War II-era U.S. aircraft such as the P-47 Thunderbolt, P-51 Mustang, and the Korean-era U.S. F-86 Sabre.
• Fixed or flexible-mounted defensive armament in World War II-era bombers such as the B-17 Flying Fortress, and B-24 Liberator.
• A long-range sniper rifle, when equipped with a telescopic sight. This use was discovered by US Marine sniper Carlos Hathcock during the Vietnam War. The M2 had two traits that made this possible:

1. The M2HB has a full automatic mode activated by locking down the bolt release lever between the butterfly triggers. Full automatic fire mode is achieved by rotating a snap spring on the exterior of the buffer housing to hold the bolt release down. The M2HB can be fired dependably in single-shot mode with the bolt release up and pressing it to load each round. A skilled gunner can fire single rounds by quickly releasing the butterflies on full automatic mode. In either mode the gun is fired by pressing the butterfly trigger.
2. Its traversing-and-elevating (T & E) mechanism attached to the tripod made accurate aiming possible, by turning the traversing handwheel and elevating handwheel until the target was in the sights.

Using the Unertl scope supplied on his Winchester Model 70 .30-06 sniper rifle and a mounting bracket of his own design, Hathcock could quickly convert the M2 into a rifle that, in single-fire mode, could accurately hit targets at up to 2500 yards--twice the range of the Winchester sniper rifle. The success of the M2 in this role led to the development of purpose-built sniper rifles, generally bolt-action, designed to fire the same .50-caliber round.

A water-cooled version of the larger M2 was used as an emplaced or vehicle-mounted anti-aircraft weapon on a sturdy pedestal mount.

Commonwealth use of the .50 was limited in the Second World War, despite it being standard armament on US-built/designed AFVs such as the M4 Sherman or M10 Wolverine that began to see use in British, Canadian, Australian and New Zealand units from 1942 on. Commonwealth tank crew commanders more often than not deleted the .50 altogether as being of limited use, given three factors. First, the weapon was an anti-aircraft weapon, and Allied aerial superiority rendered it unnecessary. Second, in order to employ the weapon against ground targets, the commander had to exit the turret and expose himself to enemy fire. Finally, Commanders, especially in Italy, also found that the gun caught on low-hanging trees and vines and posed a danger to the crew commander's head and face.

Variants and derivatives

M2 variants

The basic M2 was deployed in US service in a number of subvariants, all with separate complete designations as per the US Army system. The basic designation as mentioned in the introduction is Browning Machine Gun, Cal. .50, M2, with others as described below.

The development of the M1921 water-cooled machine gun which led to the M2, meant that the initial M2s were in fact water-cooled. These weapons were designated Browning Machine Gun, Cal. .50, M2, Water-Cooled, Flexible. There was no fixed water-cooled version.

Improved air-cooled heavy barrel versions came in three subtypes. The basic infantry model, Browning Machine Gun, Cal. .50, M2, HB, Flexible, a fixed developed for use on the M6 Heavy Tank designated Browning Machine Gun, Cal. .50, M2, HB, Fixed, and a "turret type" whereby "Flexible" M2s were modified slightly for use in tank turrets. The subvariant designation Browning Machine Gun, Cal. .50, M2, HB, Turret was only used for manufacturing, supply, and administration identification and separation from flexible M2s.

Specific aircraft versions were also developed, and these subvariants are discussed in the following paragraph along with the AN/M2.

AN/M2, M3, XM296/M296, and GAU-10/A

The M2 machine gun was heavily used as a remote fired fixed weapon, primarily in aircraft, but also in other applications. For this a variant of the M2 was developed (sometimes seen under the designation AN/M2, but it is important to note that there were .30 and .50 caliber weapons with this designation), with the ability to fire from a solenoid trigger. For aircraft mounting some were also fitted with substantially lighter barrels, permitted by the cooling effect of air in the slip-stream. The official designation for this weapon was Browning Machine Gun, Aircraft, Cal. .50, M2 followed by either "Fixed" or Flexible" depending on whether the weapon was used as a fixed forward firing gun or for use by an airplane's crew, such as a waist gun position on a B-17.

The M3 was a more purpose built variant for remote firing use, that also featured a higher rate of fire. This weapon was used on the XM14/SUU-12/A gun pod.

The XM296/M296 is a further development of the M2/M3 machine gun for remote firing applications, and is currently only used in an armament system for to the OH-58 Kiowa Warrior helicopter. The M296 differs from previous remote firing variants primarily in the lack of bolt latch allowing for single shots.

The GAU-10/A (NSN or National Stock Number 1005-01-029-3428) has been identified as a member of the Browning M2 family through its inclusion in the June 2000 issue of Countermeasure (Vol 21, No 6, available online [https://crc.army.mil/MediaAndPubs/magazines/countermeasure/2000_issues/cmjun00.pdf here]). Countermeasure is published by the Army Ground Risk Management Team, and identifies important issues that soldiers should be aware of with regards to risk management and safety. Beyond this connection, there is no specific information on the GAU-10/A, and it is odd that the only online reference would be from a US Army publication as this is a USAF designation.

XM213/M213, XM218, GAU-15/A, GAU-16/A, and GAU-18/A

The XM213/M213 was a modernization and adaptation of existing .50 caliber AN/M2s in inventory for use as a pintle mounted door gun on helicopters using the M59 armament subsystem.

The GAU-15/A, formerly identified as the XM218, is a lightweight member of the M2/M3 family. The GAU-16/A was an improved GAU-15/A with modified grip and sight assemblies for similar applications. Both of these weapons were used as a part of the A/A49E-11 armament subsystem.

The GAU-18/A, is a lightweight variant of the M2/M3, and is used on the USAF's MH-53J Pavelow II and HH-60 Pave Hawk helicopters. These weapons do not utilize the heavy barrel, and are typically set up as left-hand feed, right-hand charging weapons. In this configuration the gun is fitted with a chute adapter attached to its left hand feed pawl bracket. Thus, the weapon can receive ammunition through a feed chute system connected to internally-mounted ammunition cans. Originally designed to accommodate 1,700 rounds, these cans have since been modified due to space constraints, and now hold about half that amount. However, many aerial gunners find the chute system cumbersome, and opt to install a bracket accommodating the 100-round cans instead (as on the model pictured to the right).

GAU-21/A and M3P

The FN produced M3 series is also in U.S. military service in two versions. One being a fixed remote firing version, the FN M3P, used on the Avenger Air Defense System. The U.S. Army would appear to use this designation for the weapon.

The M3M flexible machine gun has been adopted by the USAF and the USN under the designation GAU-21/A for pintle applications on helicopters.

M2 E-50 (M2E50)

A long overdue upgrade program for existing infantry M2s and other M2s currently in U.S. Army service, the E50 finally provides a: Quick Change Barrel (QCB) capability, a rail accessory mount, an improved flash hider and a manual safety.

The E50 designation initially appeared to be within the bounds of the normal U.S. Army designation system. However, it later turned out that the term was in fact a developmental project that stands for Enhanced 50, as in enhanced .50 caliber machine gun. Developed primarily as a conversion kit for existing weapons, it is likely that new production machine guns will be built to this standard. In later U.S. Army briefings, this variant has been referenced as the M2E2 or M2A1.

International usage

The M2 family has also been widely used abroad, primarily in its basic infantry configuration. A brief listing of foreign designations for M2 family weapons follows:

Country	NATO Member	Designation	Description
Argentina	No	M2HB	12.7 × 99 mm Browning M2HB machine gun
Australia	No	M2HB-QCB	12.7 × 99 mm Browning M2HB machine gun (also manufactured locally under license by ADI)[2]
Austria	No	üsMG M2	12.7 × 99 mm Browning M2HB machine gun
Belgium	Yes	FN M2HB-QCB	12.7 × 99 mm Browning M2HB machine gun, used as infantry weapon, IFV mounted gun and as tank's AA gun
Bosnia-Herzegovina	No
Brazil	No	Mtr .50 M2 HB "BROWNING"	12.7 × 99 mm Browning M2HB machine gun
Cambodia	No	M2	12.7 x 99 mm Browning M2HB machine gun
Canada	Yes	M2	12.7 × 99 mm Browning M2HB machine gun
Chile	No	FN M2HB-QCB	12.7 × 99 mm Browning M2HB machine gun
Denmark	Yes	M/50	12.7 × 99 mm Browning M2HB machine gun
Germany	Yes	MG50-1	12.7 × 99 mm Browning M2HB machine gun
Iceland	Yes	vélbyssa	12.7 × 99 mm Browning M2HB machine gun
India	No	M2HB	12.7 × 99 mm Browning M2HB machine gun in limited quantities
Israel	No	מק"כ ("MAKACH")	12.7 × 99 mm Browning M2HB machine gun, used as infantry weapon, IFV mounted gun and as tank's coaxial gun
Ireland	No	Infantry Support, HMG & Air Defence.
Japan	No	12.7 mm重機関銃M2 (Licensed by Sumitomo Heavy Industries)	12.7 × 99 mm Browning M2HB machine gun, used as IFV mounted gun and as tank's coaxial gun
South Korea	No	K6	a clone of 12.7 × 99 mm Browning M2HB QCB machine gun (manufactured by S&T Dynamics)
Spain	Yes	Ametralladora Pesada M-2 HB	12.7 × 99 mm Browning M2HB machine gun
Norway	Yes	M/50	12.7 × 99 mm Browning M2HB machine gun
Sweden	No	Tksp 12,7 (Licensed by Bofors)	12.7 × 99 mm Browning M2HB machine gun
Thailand	No	ปืนกล 93	12.7 × 99 mm Browning M2HB machine gun
United Kingdom (British Army)	Yes	L2A1	12.7 × 99 mm Browning M2HB machine gun
United Kingdom	Yes	L6, L6A1	12.7 × 99 mm Browning M2 HB machine gun; ranging gun for the L7 105 mm tank gun on the Centurion tank
United Kingdom	Yes	L11, L11A1	12.7 × 99 mm Browning M2HB machine gun; ranging gun
United Kingdom	Yes	L21A1	12.7 × 99 mm Browning M2HB machine gun; ranging gun for the 120 mm tank gun on the Chieftain tank
United Kingdom	Yes	L111A1	12.7 × 99 mm Browning/FN M2HB QCB machine gun (built under license by Manroy[3])
Switzerland	No	Mg 64	12.7 × 99 mm Browning M2 HB machine gun

See also

• MG 131 machine gun, German rival to the M2 Browning
• XM312, proposed future replacement gun for the M2HB
• List of individual weapons of the U.S. Armed Forces
• List of crew-served weapons of the U.S. Armed Forces

References

• Gresham, John D. “Weapons”. Military Heritage. December 2001. Volume 3, No. 3: 22, 24, 26, 28, 30 (John Browning’s (M2) .50-caliber).
• [https://www.doctrine.usmc.mil/signpubs/w3151.pdf MCWP 3-15.1: Machine Guns and Machine Gun Gunnery]

External links

• Aircraft Gunnery_.50 cal.
• M2 .50 Caliber Machine Gun at Federation of American Scientists
• Browning M2HB & M2HQCB (USA)
• M2 .50 cal. Machine Gun at Olive-Drab.com
• Quad-50 M2 .50 cal. Machine Gun at Olive-Drab.com
• Video of a CG M2 showing the inner workings as it goes through the firing cycle.
• Browning M2 .50 Caliber Machine Gun at Gary's Olive Drab Page

United States infantry weapons of World War II and Korea
Side arms
Colt M1911/M1911A1 | M1917 revolver | Smith & Wesson "Victory" revolver
Rifles & carbines
Springfield M1903 | M1 Garand | M1 Carbine | M1941 Johnson | Browning Automatic Rifle (BAR)
Submachine guns
Thompson ("Tommy Gun") M1928/M1/M1A1 | M3 "Grease Gun" | Reising M50/M55 | United Defense M42
Machine guns & other larger weapons
Browning M1917 | Browning M1919 | Johnson LMG | Browning M2 HMG | Bazooka | M2 flamethrower
Cartridges used during World War II and the Korean War
.45 ACP | .38 Special | .30-06 Springfield | .30 Carbine | 9 mm Luger | .50 BMG

•  • [ e] Modern (post Korean War) UK infantry weapons
Side-arms (Self-loading Pistols)	Browning L9A1 • L105A1 • L107A1 • L102A1 (Compact)
Rifles, Carbines, & LSWs	L1A1 SLR • SA80 series (L85 IW, L86 LSW, L22A1) • L108A1, L110A1 (Para) • L101A1 • M16/A1/A2 • L119A1 (Diemaco SFW) • L100A1
Sniper Rifles	L42/A1 • L96/A1 • L115A1 • L82A1 • AW50F
Submachine guns	L2A1 to L2A3, L34A1 • L80A1, L90A1 • L91A1, L92A1
Shotguns	L32A1 • L74A1 (Remington 870 Wingmaster)
Machine-guns & other larger weapons	L4 • L7 "GPMG" • L2A1 Heavy Machine Gun • L17A1/A2 • LAW 80 • L14/A1 • L2A1 (ILAW) • L9A1 51 mm Mortar • L16/A1 81mm Mortar • MILAN • Javelin
Modern cartridges used	5.56x45mm NATO (.223 Remington) • 7.62x51mm NATO (.308 Win) • 12.7 x 99 mm NATO (.50 BMG) • .338 Lapua • 9 mm Luger • 12 gauge